The present invention relates to electronic equipment, and more particularly to electronic equipment installed outdoors.
Outdoor equipment enclosures for North America must successfully complete the standards of North America. Particularly, it is necessary to pass the following three tests relating to waterproofing, which are described in “Generic Requirements for Electronic Equipment Cabinets”, Telcordia Technologies, March 2000, GR-487-CORE issue 2, Section 3.28. Incidentally, Wind Driven Rain test is the most severe of the three tests.
1. Wind Driven Rain Test
After water spraying on the front surface, right surface, and left surface of an enclosure for 30 minutes each with a rainfall intensity of 150 mm/hr and a wind speed of 31 m/sec, the amount of water penetrating into the enclosure shall not exceed 1 cm^3 (cm3) (1 gram of water) per 0.028 m^3 (m3) (1 ft^3 (ft3)).
2. Rain Intrusion Test
Water droplets accumulated in the surface grooves and the door frame shall not enter the enclosure immediately after heavy rain. After water spraying on the front surface and the two side surfaces for 15 minutes each, the amount of water penetrating into the enclosure shall not exceed 1 cm^3 (cm3) (1 gram of water) per 0.028 m^3 (m3) (1 ft^3 (ft3)).
3. Lawn Sprinklers Test
After simulation of sprinkler water spraying at a downward angle of 45 degrees on the front surface and the two side surfaces for 15 minutes or 45 minutes in total, the amount of water penetrating into the enclosure shall not exceed 1 cm^3 (cm3) (1 gram of water) per 0.028 m^3 (m3) (1 ft^3 (ft3)).
In addition to the waterproof standard described above, the outdoor equipment enclosure for North America should meet the requirement that an electronic component housed therein can easily be replaced. In other words, the enclosure should have a structure capable of replacing an internal unit including an electronic component within the enclosure, instead of replacing the whole equipment, for the maintenance and replacement of the equipment. This is also the specification that allows the installation of the enclosure first and then the installation of the internal unit afterwards.
Further, from the point of view of the cost and weight, the material of the enclosure is preferably resin. However, it is difficult for a resin seal enclosure to fully achieve radiation performance. Hence, it is necessary to ensure the radiation performance by providing an opening in the resin enclosure through which a radiation fin of a heat sink thermally connected to the electronic component, is partially exposed to the outside of the resin enclosure. Here, the heat fin may be splashed with water, but the water penetration into portions other than the radiation fin is not allowed.
Further, in general, the electronic component and the heat sink are connected by a thermally conducted sheet. This makes it difficult to remove only a board in which the electronic component is mounted in the maintenance and replacement of the electronic component. Thus, the replacement of the electronic component should be done by removing the electronic component together with the heat sink. The unit of replacement is called an internal unit.
US 2009/0059534 discloses electronic equipment that can facilitate heat conduction from the inside to the outside of an enclosure in which an internal unit can be replaced. The enclosure structure of the electronic equipment is provided with a heat sink for releasing the inside heat. The heat sink has a heat radiation surface exposed from the bottom of the enclosure to increase the efficiency of releasing the heat from the inside to the outside of the enclosure. A canopy structure is provided below the radiation fin in order to prevent water from entering into the enclosure. In addition to the canopy structure, the electronic equipment has a structure in which a rib formed around the entire periphery of the opening for the heat sink of the case is fitted into a groove formed around the entire periphery of the heat sink, sufficiently providing the waterproof performance without using packing between the case and the heat sink. However, this structure requires eight screws to mount the internal unit. Thus, the replacement of the internal unit should be done by removing all the eight screws and tightening them again. Further, the internal unit is not fixed to the case without the screws tightened, and is likely to fall down in the replacement operation. Thus, the replacement performance is not good.